Improvement in electric thermostats



E. J. FROST.

Electric Thermostats.

No. 165,413, Patentedluly13,l875.

I III III- I .7

iglitmssrs j 69w glimmer 42 M M 'T UNITED STATES PATENT OFFICE.

EDWARD J'. FROST, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR OF ONE- IIALFHIS RIGHT TO JACOB HOEHNLEN, OF SAME PLACE.

IMPROVEMENT IN ELECTRIC THERMOSTATS.

tipecificaiion forming part of Letters Patent No. 165,413, dated July13,1875; application filed December 24, 1874.

To all whom it may concern Be it known that I, EDWARD J'. FROST, of thecity and county of Philadelphia and State of Pennsylvania, have inventeda new and useful Improvement in Electro Thermostatic Fire-Alarms; and Ido hereby declare the following to be a clear and exact description ofthe nature thereof, sufficient to enable others skilled in the art towhich my in vention appertains to fully understand, make,

and use the same, reference being had to the accompanying drawingsmaking partof this specification, in which- Figure l is a face view ofthe device embodying my invention. Fig. 2 is a side elevation thereof.Fig. 3 is a view of the under side thereof. Fig. 4: is a transversesection in line 00 .T, Fig. 1.

Similar letters of reference indicate corresponding parts in the severalfigures.

The object of my invention is to produce a thermostat occupying butsmall space, fully protected from dust, &c., and easily adjustable. Tothis end I take a thermostatic strip of any two metals of dilferentrates of expansion, and coil the same into a flat spiral, attaching theinner end of the spiral to a screw which forms at once thesupport of andmeans of adjustment of the sprin The free end of the spiral is in.contact with or corn tiguous to (depending on whether the circuit beenopen or closed one) an insulated c0n-- tact-point.

The spiral is protected by a cap or box, having a groove in one side,through which the free end of the spiral projects.

Referring to the drawings, A represents the base-plate, which may bemade of any suitable non-conducting material, and supporting the metalplate 13 in which is mounted the pin (J. From the plate B there rise thebinding screw or post D, and the insulated binding screw or post E. Frepresents a compound strip, which is made of two or more differentmetals, or other materials havin g conducting qualities which willexpand and contract unequally, due to the effects of an increase ordecrease of temperature. This strip is wound into a flat spiral, and hasone end secured to the pin 0, and the other or free end is adapted tocome in contact with a platinum-point, G, on the post E, or a projection thereon.

In the drawing, I show this form of thermostat arranged with circuits,and in the m ethodfully set out in my patent No. 156,560, of November,3, 1874, to which reference is made for a full description of the alarmmechanism and circuits herein shown.

In order that the thermostat may properly control the circuits at anypredetermined temperature, the pin 0 is adapted to be turned, and heldin position by a set-screw, or otherwise.

In the present case the under side of the plate B is chambered orhollowed, and graduated, and the pin 0 carries an index. one portion ofwhich is formed with a slotted are for the passage of theadjusting-screw, said index moving in the chamber or hollow of the plateB, so as to be concealed therein, whereby the same is not accessible,and the adjustment may remain unknown to improper parties.

Another advantage of this system of circuits is that if the wires aredetached or out either by accident or design, or the thermostat isinjured, and its efficiency is destroyed, the alarm will be given, andthe location of the accident known. The lines or circuits can always bekept in proper order.

A box or casing, M, will be provided for inclosing the compound strip,which protects the strip from dust or dirt, while allowing the air fullinfluence thereon.

It is evident that by changing the position of the contact-point, thisthermostat may be used to break a closed circuit or close an opencircuit.

Having thus described my invention, what I claim as new, and desire tosecure by Letters Patent, is-- 1. The thermostat consisting of acompound strip formed into a flat spiral, a central adjustingscrew, andthe casin g or covering, substantially as set forth.

2. The combination, with the spiral compound strip and central adjustingscrew, ot the index plate and index concealed in a hollow in the base ofthe thermostat, substautially as set forth.

EDWARD J. FROST. Witnesses:

JOHN A. Wrnnnnsnnm, A l. GRAN'L

